Polyamide resin is excellent in the chemical resistance, mechanical strength, heat resistance, abrasion resistance and the like and is widely used for electric-electronic parts, machine parts and automobile parts. However, this resin is disadvantageously poor in the impact strength. On the other hand, a rubber-reinforced styrene-based resin such as HIPS (high-impact styrene copolymer resin), ABS resin (acrylonitrile-butadiene-styrene copolymer resin), AES resin (acrylonitrile-ethylene-propylene-based rubber-styrene copolymer resin) and AAS resin (acrylonitrile-acryl-based rubber-styrene copolymer resin) is excellent in impact strength and shapability and is also widely used for automobile parts, office appliance parts, electric parts and the like, but this resin is disadvantageously inferior in chemical resistance and abrasion resistance.
In order to mutually redeem these disadvantages of respective resins, a blend of polyamide resin and ABS resin has been proposed (see, for example, Japanese Examined Patent Publication (Kokoku) No. 38-23476). However, compatibility between polyamide resin and ABS resin is low and therefore, a technique of copolymerizing an unsaturated carboxylic acid with styrene or acrylonitrile and blending the obtained unsaturated carboxylic acid-modified copolymer as a compatibilizer to the polyamide resin and ABS resin has been proposed (see, for example, Japanese Examined Patent Publication (Kokoku) No. 7-84549). With such an improvement in the compatibility, the impact strength is also enhanced to a certain extent.
However, with recent progress in increasing the size and reducing the thickness of home appliance parts, automobile parts and the like, a polyamide resin/rubber-reinforced styrene-based resin composition, particularly, a polyamide resin/ABS resin composition, excellent in the fluidity as well as in the impact strength is demanded to enhance the shaping cycle and increase the productivity.
To meet this requirement, a technique of using an unsaturated carboxylic acid-modified copolymer having a reduced viscosity within a limited range as a compatibilizer and thereby balancing the impact strength and the fluidity has been proposed, but its effect is not yet satisfactory (see, Japanese Unexamined Patent Publication (Kokai) No. 2000-17170).
It could therefore be advantageous to solve those problems in the polyamide resin/rubber-reinforced styrene-based resin composition, and to provide a polyamide resin/rubber-reinforced styrene-based resin composition, particularly, a polyamide resin/ABS resin composition, excellent in balance between impact strength and fluidity as well as in heat resistance, chemical resistance and paintability.